T. Kohout1,2,¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹Department of Physics, University of Helsinki, Helsinki, Finland
²Institute of Geology, Academy of Sciences of the Czech Republic, Prague, Czech Republic

X-ray microtomography (XMT), X-ray diffraction (XRD), and magnetic hysteresis measurements were used to determine micrometeorite internal structure, mineralogy, crystallography, and physical properties at μm resolution. The study samples include unmelted, partially melted (scoriaceous), and completely melted (cosmic spherules) micrometeorites. This variety not only allows comparison of the mineralogy and porosity of these three micrometeorite types but also reveals changes in meteoroid properties during atmospheric entry at various velocities. At low entry velocities, meteoroids do not melt and their physical properties do not change. The porosity of unmelted micrometeorites varies considerably (0–12%) with one friable example having porosity around 50%. At higher velocities, the range of meteoroid porosity narrows, but average porosity increases (to 16–27%) due to volatile evaporation and partial melting (scoriaceous phase). Metal distribution seems to be mostly unaffected at this stage. At even higher entry velocities, complete melting follows the scoriaceous phase. Complete melting is accompanied by metal oxidation and redistribution, loss of porosity (1 ± 1%), and narrowing of the bulk (3.2 ± 0.5 g cm⁻³) and grain (3.3 ± 0.5 g cm⁻³) density range. Melted cosmic spherules with a barred olivine structure show an oriented crystallographic structure, whereas other subtypes do not.

Reference
Kohout et al. (in press) Density, porosity, mineralogy, and internal structure of cosmic dust and alteration of its properties during high-velocity atmospheric entry. Meteoritics & Planetary Science
[doi:10.1111/maps.12325]
Published by arrangement with John Wiley & Sons

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Weiming Cheng, Jiao Wang, Cong Wan

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Reference
Cheng W, Wang J and Wan C (2014) Morphometric Characterization and Reconstruction Effect Among Lunar Impact Craters. Earth, Moon, and Planets 111:139.

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N. Biver¹ et al. (>10)*
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¹LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, 5 place Jules Janssen, 92195 Meudon, France

A spectral survey in the 1 mm wavelength range was undertaken in the long-period comets C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy) using the 30 m telescope of the Institut de radioastronomie millimétrique (IRAM) in April and November−December 2013. We report the detection of ethylene glycol (CH₂OH)₂ (aGg’ conformer) and formamide (NH₂CHO) in the two comets. The abundances relative to water of ethylene glycol and formamide are 0.2–0.3% and 0.02% in the two comets, similar to the values measured in comet C/1995 O1 (Hale-Bopp). We also report the detection of HCOOH and CH₃CHO in comet C/2013 R1 (Lovejoy), and a search for other complex species (methyl formate, glycolaldehyde).

Reference
Biver et al. (2014) Complex organic molecules in comets C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy): detection of ethylene glycol and formamide. Astronomy & Astrophysics 566:L50.
[doi:10.1051/0004-6361/201423890]
Reproduced with permission © ESO

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